He claims that his conscience "got the better" of him.
"It was all just so wrong," he told the Mail. "I wasn't a broker myself at this stage, but I had a business link to the firm."
When investors began to get suspicious, the firm of brokers tried to remove all evidence of the scams. However, the whistleblower kept the "Barclays leads" without the firm's knowledge.
The Information Commissioner's Office can impose fines of up to £500,000 on organisations that fail to protect customer data in line with the Data Protection Act.
Meanwhile, the Financial Conduct Authority (FCA) has the power to levy fines in the millions of pounds in data loss cases.
In 2012, Barclays received a fine of £59.5 million from the Financial Services Authority (FSA), the previous incarnation of the FCA, for misconduct relating to the reference rates at which banks lend to each other, known as London Interbank Offered Rate (LIBOR).